1890.] 127 rRyd er. 



decrease of the number of polar bodies in the eggs of many partheno- 

 genetic forms, in which the period of growth of the eggs is often short- 

 ened, and where the physiological function of the chromatin in the con- 

 structive metabolism of the egg is exerted over a less prolonged period. 

 The result is that the exhausted chromatin or nucleoplasm which is to be 

 expelled from some parthenogenetic ova is just half that of the other 

 type requiring fertilization. Such a separation and regeneration leave 

 enough chromatin or nucleoplasm behind to initiate development by 

 beginning a spontaneous and continuous fission of the egg without the 

 access of the male element. This I believe, however, to be only a partial 

 explanation of the causes leading to the expulsion of the polar bodies, 

 since the genesis of the ovum itself remains unexplained. The specializa- 

 tion of the ovum and its hypertrophy as a cell is connected in another 

 way with the operation of the processes of continuous growth, and with 

 the evolution of the primseval form of germs which were unquestionably 

 flagellate. That the ovum is the most specialized cell of the two kinds of 

 sexual cellular types found in Metazoa there can be no doubt. 



If it is true that the only thing that stands in the way of the develop- 

 ment of any cell of the body into a germ is its physiological and morpho- 

 logical specialization, then the egg with its mass of cytoplasm in excess of 

 that of any cell in the body is certainly a morphologically and physiologic- 

 ally specialized cell-unit. The expulsion of the polar bodies brings it back to 

 an unspecialized condition, in which its nucleus (the female pronucleus) 

 no longer bears any imprint of its former physiological specialization 

 which it had acquired during the elaboration of its bulky mass of cyto- 

 plasm. 



The history of the spermatic body, or cell, is exactly the reverse of the 

 preceding. If protandrously developed, karyokinetic or fissive processes 

 go on more rapidly from the start than processes of growth through con- 

 structive metabolism and spermatozoa result. If the spermatic body is 

 produced through a protogynous process and from large cells simulating 

 ova, the fissive tendency again finally obtains the upper hand, but only 

 after a certain maximum size of the female cells is reached, when they 

 may be recognized as ova. The tendency towards maleness is thus con- 

 stantly against any persistence of a condition favoring constructive meta- 

 bolism in the direction of the elaboration of cytoplasm. In fact, so rap- 

 idly does the fissive process go on, that the nuclei of the spermatic or male 

 cells have no opportunity to acquire any physiological function, such as 

 that enjoyed by the nucleus of the egg. The tendency in the male cells 

 is rather to intensify the tendencies of metabolism towards the elaboration 

 of chromatin only, carrying the latter process so far that little or no field 

 of cytoplasm finally remains in which fission or nuclear movement can 

 occur ; nay, many instances are known where even the remaining remnant 

 of the cytoplasm is cast off from the spermatozoon previous to maturity, 

 this being in exact contrast again with the extrusion of a part of the egg's 

 chromatin as polar bodies. The rapidity of the successive processes of 



